Fuel tanks are used to supply fuel to internal combustion engines. For example, 4WD (four-wheel-drive) vehicles and FR (front engine, rear wheel drive) vehicles use a so-called saddle type fuel tank, the bottom of which is upwardly recessed at a center portion in the width direction of the vehicle in order for the fuel tank to avoid physical interference with a propeller shaft, which extends down the middle of the vehicle.
A saddle fuel tank generally is divided into a first reservoir for reserving fuel and a second reservoir for reserving fuel. Each of the first reservoir and the second reservoir is equipped respectively with a fuel pumping system. Accordingly, in comparison with fuel tanks for use in 2WD (two-wheel-drive) vehicles, a saddle fuel tank requires two fuel pumping systems, and a problem is encountered in that a saddle fuel tank tends to be more costly and larger in size.
Thus, for example, there is known a fuel tank level equalizer system, as disclosed in Japanese Laid-Open Patent Publication No. 10-061515. As shown in FIG. 11 of the accompanying drawings, the fuel tank level equalizer system includes a fuel tank 1 having two separate sections 1a, 1b, and operates to maintain equal fuel levels in the separate sections 1a, 1b via a siphon 2.
The separate section 1b houses therein a fuel pump module 3, which has an outlet connected to a bypass pressure regulator 4. The regulator 4 has an outlet connected to a conduit 5 through which liquid fuel is supplied to a nozzle 6a of a jet pump 6. The jet pump 6 is operated by liquid fuel that is supplied to the nozzle 6a, thereby transferring the fuel through the interior of the siphon 2 from respective fuel pickups 2a, 2b of the siphon 2.
Accordingly, the fuel levels in the separate sections 1a, 1b are equalized through the siphon 2, whereby a single fuel level sensor 7 can monitor all of the fuel levels in the vehicle.
In the above fuel tank 1, each of the fuel pickups 2a, 2b is equipped with a flow valve assembly, not shown, which is actuated by a filter and a diaphragm. The filter is made of a flexible material having small openings or pores therein. The filter, when wetted, prevents air from flowing therethrough due to a capillary action of the liquid fuel. In the event that liquid fuel is not present in the inlets of the fuel pickups, air is prevented from flowing therethrough by a liquid capillary seal of the filter.